The failure to detect, find and correct minor roof deterioration in the earliest stages is considered the greatest cause of premature roof failure. This is particularly true of roofing materials applied on low-slope or flat roofs. Costly roofing problems are often the result of design deficiencies or faulty application of the roof system. Even when properly designed and applied, all roofing materials deteriorate from exposure to the weather at rates determined largely by the kind of material and the conditions of exposure.
Several methods have been used to try and locate roof leaks after they have occurred. This is becomes a particular problem for inverted roof assembly membranes (IRMA) roofs where the roof membrane is typically bonded to a concrete deck and any leak detection system needs to be located on top of the membrane which is usually covered with a thin layer of water. The detection system must then locate any membrane breach through the water layer to the deck below while avoiding other paths to ground formed by roof drain, pipe penetrations, and metal flashings.
Electric field vector mapping uses a wire loop around the perimeter of the roof surface to introduce an electric potential between the structural deck and a selected roof area which is sprayed with water. The electric field potential caused by a conductive path to any roof membrane damage is then located using a sensitive voltmeter and a pair of probes. The vector mapping method it limited in its ability to locate the ground fault signal when the IRMA roof includes insulation and heavy overburden such as a vegetative covering.
A roof leak monitoring system is detailed in U.S. Pat. No. 7,652,481 (Vokey) issued Jan. 26, 2010 to Detec Systems LLC discloses an arrangement for leak detection on flat roof systems using a gridded system of wire sensors whereby the X and Y wires that form a grid are alternately operated as an electric guard and then as a leak detection sensor measuring the conductivity to ground at a membrane breach through the water on the surface of the membrane. The method relies on the assumption that a breach through the membrane will be located coincidentally at an intersection of the x and y wires of the common grid section. However, where there are two breaches including a first breach close to an x grid location only and a second breach at a location next to a y grid location only can, the analysis of the voltages can result in an incorrect assessment that there is a single breach in the grid sections where the x and y wires of the grid intersect.
An improvement to this arrangement is also shown in U.S. Pat. No. 8,319,508 (Vokey) issued Nov. 27, 2012.
A yet further improvement is shown in Published US application 2014/0361796 which shows that, where a roof deck is used which has no or low electrical conductivity, a measurement system can be provided where the current is detected between a sensor on top of the membrane and a conductive layer underneath the membrane connecting the deck to the membrane such as an adhesive.
The disclosure of the above Vokey patents is incorporated herein by reference or may be referred to for further details of the subject matter claimed herein.
A more recent roof leak monitoring system is detailed in U.S. Pat. No. 8,566,051 issued Oct. 22, 2013, to Gunness which describes a system for detecting and locating a leak through a membrane that includes a detector array and computer. The detector array includes a boundary wire loop, sensors, and leads. The boundary wire loop surrounds the area of the membrane to be tested and generates electrical tension on the surface of the membrane. The sensors are laid out in a sensor array and are placed on top of the membrane and within the boundary wire loop. The sensors are encased in a plastic covered cable or form individual wires which have open ends for their terminations so as to define a cable so that the sensors made by the open terminations form a chain. Each sensor communicates individually with the computer and the signals from the sensors are used by the computer to perform vector mapping that detects and locates leaks through the membrane. This is an automated form of vector mapping which relies on a uniform and continuous covering of water over the membrane to locate breaches accurately.
All of the above methods are usually employed to assist in locating roof leaks on IRMA assemblies.